Gas-operated automatic firearm



D. M. WILLI AMS ET AL GAS-OPERATED AUTOMATIC FIREARM May 16, 1944.

Filed Jan. 13, 1940 3 Sheets-Sheet 2 4 3 WW8 6 mm WWW w w w m WM w W 5 77 g 2 9 %& Q. @%/\A\\\\\\\\\\\\\AA%% D. M. WILLIAMS ET AL GAS-OPERATED AUTOMATIC FIREARM May 16, 1944.

Filed Jan. 13, 1940 3 Sheets-Sheet 3 J a a a fly [j #7 9293 Ir ma 0 b 0.0% e 0 av v WW /WW w b 8 7 mm M 6 3 J1 4 w as... May is. 1944 2,348,872

David M. Williams and William C. ltoemer, New Haven, Conn., assignors to Western Cartridge Company, New Haven, Conn, a corporation of Delaware Applicatioglanuary 13, 1940, Serial No. 313,650

2 Claims. (01. 42-3) This invention relates to improvements in automatic firearms and more particularly to that type of automatic firearm which is operated by gas-pressure developed by-the flringot a cartridge and acting upon a piston for effecting the ejection of a fired cartridge and for theinsertion of a fresh cartridge. One'of the objects of the present invention is to provide an automatic firearm of the type referred to which is adapted for military use by having means for mounting a bayonet, but which does not require excessive length and its resultant objectionable weight.

Another objectof the present invention is to provide a superior automatic firearm of the gasoperated type wherein the gas-cylinder may be conveniently located beneath the barrel without making it necessary to undulyextendthe length of the firearm in order to accommodate a bayonet.

A further-object of the present invention is to provide a superior firearm of the type above re-.-

ferred to with superior means for mounting a bayonet. r 1

Still another object. of the present invention is to provide a superior gas-operated automatic firearm having a superior construction and ar'rangev immediately adjacent to the combined cylinderand bayonet-mounting-fixture;

Fig. 3 is a horizontal sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is a transverse sectional view taken on the line l 4 of Fig. 2;

Fig. 5 is a similar view taken on the line 5-5 of Fig. 2;

Fig. 6 is a transverse sectional view taken on the line 5-8 of Fig. 2; a

Fig. '7 is a similar view taken. on the line 'l-l' of Fig.

Fig. 8 is a broken perspective view of the piston together with a portion of the actuating-rod;

Fig, 9 is a perspective view partly in vertical central-longitudinal section of the'eombined cylinderand bayonet-mounting fixture;

Fig. 10 is aperspective view of the gas-cylinder; Fig. 11 is a perspective-view of the cylinderretainer;

Fig. 12 is a fragmentary perspective view of a portion or the barrel;

ment of parts whereby the gas-cylinder and associated parts may be readily cleaned.

A'sti ll further object of the present-invention is to provide a firearm of the type referred to in which the gas-cylinder may be readily demou'nted and replaced.

Another object is to provide a superior automatlc firearm in which a gas-cylinder is removably organized therewith by means ofsuch charact-er as may be released without requiring the use of any special tools and removed by the use or I. the casing of;a cartridge.

With the above and other objects in .view, as

will appear to those skilled in the art from the present disclosure, this invention includes all features in the said disclosure which are novel over the prior art and which are not claimed in any separate application.

In the accompanyingdrawings, in which certain modes of carrying out the present invention are shown for illustrative purposes:

firearm embodying the presenti inventionn may assume; Fig. 2 is an enlarged fragmentary view partly in side elevation andpartiy in'vertcalcentrallongitudinal section of the portion of the firea m Y Fig. 13 man enlarged fragmentary view mainly in side elevation and partly in vertical centrallongitudinal section of the portion of the firearm immediately adjacentto the cylinderand bayonet-mounting fixture and illustrating another form of coupling-meansv for securing the said fixture in place;

Fig. 14 is atransverse sectional view taken on the line ll-il of Fig. 13; 1

Fig. 15 is a fragmentary view in side elevation of the portion of the firearm adjacent the cylinderand bayonet-mounting fixture and illustrating still another form of coupling-means for securing the said fixture in place: and

Fig. 16 is a transverse sectional view taken on .the line iB-IB of Fig. 15.

The particular gas-operated automatic firearm herein chosen for the illustration of the present invention in' Figs. 1 to 12 inclusive includes a receiver l5 from which forwardly projects a barrel l6 rigidly secured to the said receiver and providedwith the usual axial passage or bore ll through which the projectile and accompanying burning or burnt gases may pass forwardly. Attached to the-barrel l6 bya customary band 18 is a stock H which is also secured to the receiver [5 in any approved manner. a

, As shown in Figl, an action-slide 20 is mounted with capacityfor longitudinal'reciprocating movement with respect to the receiver and cylinderchnnected at its upper end to the rear end of a breech-bolt 22 movable within the receiver I5. Extending rearwardly from the rear end of the action-slide is a spring-plunger 23 encircled by a breech-bolt-closing spring 24 serving to restore the breech-bolt 22 to its forward or closed position, as shown in Fig. 1, after the said breechbolt has been thrown rearwardly by thedischarge of the firearm in a manner as will hereinafter appear.

As is usual in automatic firearms, the rearward travel of the breech-bolt 22 effects the extraction and ejection of a fired cartridge. Upon its return travel under the urge of the breech-balk closing spring 24, the breech-bolt 22 acts to insert a fresh cartridge into the firing-chamber of the firearm preparatory to another cycle of operation under the control of a trigger 25.- The said trigger 25 is located within a trigger-guard 26' which forms a rigid feature of a trigger-plate 21 secured in any suitable manner to the underside of the receiver I 5.

For the purpose of enabling the user of the firearm to manually retract the breech-bolt 22 an L-shaped link 28 is employed which has itsv I guided for reciprocating movement in a guide-,

groove 32 formed in, the side wall of the receiver l5. The rear end of the horizontal arm 3| of the link 28 is provided with an operating-handle 33 as shown in Fig. 1.

By reference to Fig. 4 in particular it will be noted that the piston-guide tube 43 has a por- I tion of its outer periphery seated in an arcuate I piston-guide tube' 48 in the coupling-notch 49 Operatively connected to the forward end of v Adjacent its forward end the barrel I6 is formed with a smooth cylindrically-contoured portion 38 upon which is mounted ,a combined and bayonet-mounting fixture 39 formed in its upper portion with an axial bore 49 extending through from front to rearthereof and through which the portion 38 of the barrel l6 extends. At its rear end the fixture 39 abuts against the forward face of a radially-extending annular. flange 4| forming an integral part of the barrel I6 at the junction of the main part of the said barrel and its portion 39 before referred to. The fixture 39 is securely retained against axial displacement on the portion 38- of the barrel I 6 with its rear end abutting against the flange 4|, by an annular nut 42. The nut 42 is threaded onto the externally-threaded forward end 43 of the portion 36 and is provided with radial passages 44 by means of which the nut 42 may be threaded in place by a spannerwrench or the like.

Immediately beneath the axial passage the 'cylinderand bayonet-mounting fixture 39 is formed in its lower portion with a cylinder'-re ceiving passage 45 extending in substantial parallelism with the passage 40. The cylinder-receiving passage 45 at its rear end opens into an internally-threaded socket 46 which receives the externally-threaded forward end 41 of a pistonguide tube 48 extending rearwardly from the r it will be readily apparent that the fixture 39 is eifectively coupled to. the barrel l6 against relative rotation with respect thereto. It may here be noted that the piston-guide tube 46 has axially passing therethrough the operating-rod 36 before referred to, the said guide-tube being adapted upon occasion to receive and guide the piston 31 in a manner as will hereinafter appear.

. At its forwardend the cylinder-receiving passage. 45 in the fixture 39 opens into an enlarged socket 5|| constituting an enlarged concentric portion of the passage 45 and formed in an extension 5| forwardly projecting from the forward edge of the cylinderand bayonet-mounting fixture 39. The extension 5| is of substantially U-shaped form in cross section and has the upper edges of its side arms 52-52 concaved to provide clearance for the adjacent portion of the outer periphery of the annular nut 42, as is particularly well shown in'Fig. 7. p

Intermediate its opposite ends, the cylinderreceiving passage 45 in the fixture 39 is intersected by radially-extending passages 53 and 53a located diametrically opposite to each other, the passage 53 being formed in the partition 54 existing between the axial passage 46 and the cylinder-receiving passage 45. The passage 53 is adapted to be in registration with a gas-port 55 leading radially outwardly from the bore. l1

of the barrel l6, when the cylinderand bayonetmounting fixture is secured in place on the said barrel, as is particularly well shown in Figs. 2 and-5. By reference to the figures justreferred to, it will be noted that the passage 53a is in line with and opens outwardly from the cylinderreceiving passage 45 through the outer face of the lower portion of the fixture 39, for the purpose as will hereinafter appear.

Mounted in the cylinder-passage 45 of the fixture 39 is a cylinder 56 which is formed in its inner or rear end with an axial gas-chamber 51 receiving with a sliding fit the piston 31 before referred to. Adjacent the forward end of the said gas-chamber 51 and forwardly of the piston 31 is a radial port 58 leading outwardly therefrom through'the wall of the cylinder 56 in registration with the passage 53 and gas-port 55 when the said cylinder is installed in place in the cylinder-receiving passage 45.

The forward or outer end of the cylinder 56 isformed with a head 59 through which extends diametrically-opposite radial passages 6066 intersecting an axial lightening bore 6| formed in the outer portion of the said cylinder. Imme- 56 is formed with an enlarged portion 62 located in the socket 50 in the extension 5| of the fixture 39. The said enlarged'portion 62 has its upper portion cut away for substantially on a radius corresponding to the external curvature of the cylinder 56, as shown particularly well in Figs. 7 and 10, to provide a clearance-groove 62a having sloping end walls 62b and 620. As shown in'the figures referred to, the enlarged portion 62 is cut away to provide the necessary clearance for the annular nut 42 which projects into the socket 59 and to permit the cylinder 56 to be rotated or turned substantially 90 with respect to the said tered into their complemental coupling-grooves,

annular nut and the fixture 35, for the purpose later to be described. By having a portion of the enlarged portion 52 of the cylinder 55cut away to provide the clearance-groove 52a for interfitting with the annular nut 42, thecylinder 55 is effectively prevented from being wronglyy installed, as will more fully hereinafter appear.

To the rear of the enlarged portion 52, the cylinder- 55 is provided on its outer periphery with two pairs of diametrically-opposite radially-oilsetting arcuate coupling-lugs 55-53,5l-55.

The arcuate coupling-lugs53-53 are respectively spaced from each other longitudinally of the cylinder 55 so as to form a. coupling-groove,

Similarly, the arcuate conpling-lugs 54-55 are also spacedfrom each other 55 therebetween.

to provide a coupling-groove 65 between the said coupling-lugs. The coupling-lugs 55-53 and it will beapparent that the cylinder 55 is prescribed, the port .58 thereof .will be properly registered withthe passage 53 of the. cylinderand bayonet-mounting fixture 39 and the gas-port 55 1 of the.barrel I5. By providing the cylinder 55 54-54 have their outer faces curved to' fit within the cylindrical socket 55 of the cylinderand bayonet-mounting fixture 39. s

The two pairs of coupling-lugs 55-55 and 54-55 of the cylinder 55 are respectively adapted to be rotatably entered into one of two pairs of coupling-grooves 51-51 and58-58 formed in the fixture 39 andrespectlvely located diametrically opposite to each other and being acontinuation of the curved face of the socket 55. The coupling-grooves51-51 have interposed between them a rib-like arcuate coupling-lug 59, and simiwith the clearance-groove 52a,-the saidcylinder may be installed in the cylinder-receiving passage 55 of the fixture only in such manner as to permit the cylinder 55 to be correctly turned to bring its port 58 into registration with the passage 53 and gas-port 55 previously described. -The provision of the clearance-groove 52a in the cyllarly the coupling-grooves 58-55 have interposed i between them a rib-like arcuate coupling-lug15,

which-coupling-lugs are adapted to be respectively entered into the coupling-grooves 55 and 55 of the cylinder 55. The pairs of couplinggrooves 51-51 and 55-58 have their respective inder 55 thus efiectively prevents thesaid cylinder from being incorrectly installed in the cylinder-receiving passage of the fixture 59. i Immediately enlarged portion {of the cylinder 55 is formed with diametrically-opposite radially-extending passages'13-15 adapted, when the said cylinder is installed in place in the cylinder-receiving pas-.

sage 55, to register with two diametrically-opposite radial passages 14-14 formed mule side.

arms 52-52 of the extension 5| of the fixture 59.

' The passages 15-13 and 14-14, when in registraopposite ends merged into the cylindrical socket 50. Vertically between the adjacent ends of the respective pairs of coupling-grooves 51-51 and 55-55 are clearance-grooves H and 12, as shown in Figs. 6 and 9.

- The clearance-grooves 1| and 12 are respectively adapted to provide forthe free passage of the respective pairs of coupling-lugs 55-55 and 54-55 when the cylinder 55 is axially moved into or out of position in the cylinder-receiving passage 55. When the cylinder 55 is axially moved into the cylinder-receiving passage 45 to the limit of its inward movement with the sloping end .wall 52b of the clearance-groove'52a of the said cylinder in engagement. with the annular nut 52, the pairs of coupling-lugs 53-53 and 55-55 will respectively have passed "axially through the clearancerooves 1| and 1,2. The

positioning of the cylinder 55, as just described, will bring the coupling-lugs 53-55-and 55-55 into vertical alignment with the respective coupling-grooves 51-51 and 58-55 in the fixture 55. Withthe cylinder in this position, it will be understood-that the coupling-grooves 55 and 55 thereof are also respectively in vertical alignment with the coupling-lugs 55 and 10 formed in the socket of the cylinderand bayonetmounting fixture 59. With the parts positioned as just above described, the cylinder may be rotated or turned .in a. counterclockwise direction (as viewed from the' rear: end of .the firearm) through an arc of substantially 90 to enter the respective pairs of coupling-lugs 53-53 and 55-55 into their complemental coupling-grooves 51-51 and 55-55;

The coupling-gr0oves 55 and 55 of the cylinder 55 will respectively receive the coupling-lugs 59 and 10 projecting inwardly from the socket 50 of the fixture 35. When the coupling-lugs are ention witheach other, receive a cylinder-retaining pin 15 which extends transversely of the extension 5|. of the cylinderand bayonet-mounting fixture 55, as shown in Figs. 3 and 7, when the. cylinder is properly posltione'din the said fixture. As will be apparent, the pin 15 serves to prevent the turning 01" the cylinder 55 when the said pin is assembled in place.

. The cyllnder-retainingpin 15 has rigidly secured to one end thereof a lever 15 which is normally, tinder inherent spring tension, in engagement with the adjacent side face of the cylinderand ba'yonet-mounting'fixture 38, as shown in Fig. 3. The lever 15 is formed at its outer end with an inwardly extending detentefinger 11 normally seated in a conical detent-recess 18 formed in the side iace'oi' the fixture as is clearly shown in Fig; 3 and which serves to prevent the lever, 15 from being unintentionally rotatably displaced from the position in which it is shown by full lines in Fig. 1 to that in which it is shown by broken lines in the same figure. The iorward end 15- of the lever 15 is normally seated in an arcuate retaining-slot 50 formed in the rear faceof a retaining-lug 5| projecting outwardly from the right-hand face ofthe-head 55 of the cylinder- 55. The arcuate retaining-slot 55, isswung with the axis of the pin 15 as a center to enable the forward and 1a oi the lever n to be turned into and out. of the said retaining-slot 55.

As will be apparent, the retaining-slot serves to prevent the axial displacement of, the pin. 15

but allows the'said pin to be axially bodily re movedwhen the lever 15 is swung-down into theposition inwhich it is shown by broken lines in a Fig. '1. It will be uhderstoodf that the detentfinger 11 is first removed from the 'detent-recess 18 by the point of a cartridge, or by other means,

to allow the lever 15 together with the pin 15 .to

the rear of the head 59, the"- be turned about the axis of the said pin to thereby remove its forward end 18 from the retainingslot 88 permitting the subsequent axial withdrawal of the pin 18. I

With the pin 18' removed, the cylinder 58 may be easily and readily turned by passing a cartridge-casing such as 82 (shown by broken lines in Fig. 3) through the radial passages 88-88 1 in the head 58 of the said cylinder. By means of the cartridge-casing 82, the said cylinder may be readily turned to" remove its coupling-lugs from their respective coupling-grooves in the socket 88 of the cylinderand bayonet-mounting fixture 88, to thus bring the said coupling-lugs into horizontal alignment with the clearance-grooves 1| and 12 thereof. With the coupling-lugs in horizontal alignment with the clearance-grooves as just above described, the cylinder 88 may be axially withdrawn forwardly from the cylinderreceiving passage 45 and the socket 58 for inspection, cleanin replacement, etc.

Returning to the piston 31, it will be noted that the said piston is formed at its rear end with four (more orless) radially-extending guide-ribs 83 and with a corresponding number of notches 84 separating the respective ribs 83. The ribs-88 are adapted to freely slidingly fit the piston guidetube 48 and serve to hold the piston 81 axially in place in the said guide-tube 48 when the piston 81 has been moved rearwardly out, of the gaschamber 81' and into the said guide-tube in a manner as will hereinafter appear. \I

The combined cylinder-and bayonet-mounting fixture 88 is formed on its under face adjacent the forward end thereof, with 8. depending T-shaped bayonet-coupling lug 85 which serves to securely couple the outer end of the handle bf a bayonet (not shown) to the firearm structure in any customary manner requiring no description herein. ,Adiacent its rear end, the cylinderand bay- .onet-mounting fixture 88 is also formed on its under, face with two depending ears 88-88 laterally spaced from each other to receive between them the upstanding coupling-ear 81 of a stacking-swivi 88,-which latter may be of any conventional form. To pivotally connect the Stacking-swivel 88 to the ears 88-88, the said ears and the coupling-ear 81 of the stacking-swivel 88 have passing therethrough a pivot-screw 88, which latter is threaded into one of the coupling-ears 88 depending from the fixture 88. The stackingswivel 88 requires no detailed description herein, as it may be of any conventional form andserves, in the manner customary to such stackingswivels, to allow the stacking of firearms.

' For brevity \of description, it may be stated that the breech-bolt 22 and associated parts which are actuated by the action-slide 28 are to be considered as constitutinga so-called firearm-action, in accordance'witlr-wen understood terminology in the art.

For the purpose of making clear the operation of the firearm herein chosen for illustration, let it beassumed that the piston 81 is occupying the position in which it is shown by full lines in Figs. 2 and 3 of the accompanying drawings,

under the urge of the breech-bolt-closing spring pressure back of the said projectile will escape radially outwardly through the said gas-port 88, passage 83, and port 88 into the forward end of the gas-chamber 81. The entry of gas into the gas-chamber 81 as just described, will forcibly expel the piston 81 rearwardly with the result that the actuating-rod 88, breech-bolt fl and associated parts will all be moved rearwardly against the tension of the spring 24. In this manner, the casing of the Just-fired cartridge will be ejected and the firing mechanism will be cocked, preparatory to the return movement of the breech-bolt 22, action-slide 28 and associated parts to their former position, as illustrated in Figs. 2 and 3.

As is usual in automatic firearms, the breechboit 22 after having been retired in the manner above described, will move forwardly under the urge of the breech-bolt-closing spring 24 and will insert a fresh cartridge into the cartridgechamber in the rear end of the barrel l8, preparatory to again discharging the firearm by means of the actuation of the trigger 28.

As the piston 81 moves rearwardly when the firearm is discharged, the said piston will pass rearwardly out from the gas-chamber 81 and beyond the rear edge of the cylinder 88. When the piston 81' has been completely rearwardly moved out of the gas-chamber 81 into the guidetube 48, the said piston and the forward end of the actuating-rod 88 will be guided by the said guide-tube during the course of its rearward travel. When the forward face of the piston 81 has, cleared the rear edge of the cylinder 88, the gases containedin the gas-chamber 81 will be free to escape rearwardly into the guide-tube 48 and through the notches 84 of the said piston '31, relieving the rearward pressure forwardly thereof.

When the piston :1 is being guided by the guide-tube 48, it will be understood that the ribs 88 thereof serve to position the said piston in place in the said guide-tube to insure that the said piston is guided concentrically into the gas-chamber 81 upon the forward return movement thereof, preparatory to another cycle of operation.

Instead of employing the coupling-means shown in the structure of Figs. 1' to 12 inclusive, to couple a cylinderand bayonet-mounting fixture and barrel together, a structure such as that illustrated in Figs. 13 and 14 may be employed. In the figures referred to, many features oi the structure are, in the main, the same as those illustrated in the preceding figures,- and previous-.

' 8l extends outwardly through the rear end of the fixture 8.8 and receives a key 82 fitting also in a longitudinal coupling-groove 88 formed in Now when the trigger. 28 isoperated inthe powder charge. As the projectile passes beyond the inner end of the gas-port 58, the gas-underthe outer periphery of. the barrel 18a immediately forwardly of the radial flange .lla of .the said barrel "a. As will be apparent, the

key- 82 effectively preventsthe cylinderand bayonet-mounting fixture 88 from turning or rotating on the barrel 18a when the said fixture is secured in place with its rear end seated against the forward face of the flange 41a of the said barrel l6a by the annular nut 42a, as previously described. r

In Figs. and 16 still another form of coupling-means is illustrated for coupling the combined cylinderand bayonet-mounting fixture against relative rotation with respect to the barrel of the firearm. In the figures referred to, many of the features correspond to those shown in Figs. 1 to 12 inclusive, and Where such features appear in Figs. 15 and 16 and are not otherwise designated, they bear the same reference'characters plus the reference character b." In the construction shown in Figs. 15 and 16, a cylinderand bayonet-mounting fixture 94 is employed and is provided on its rear end with two rearwardly-projecting coupling-lugs 95-95 located diametrically opposite each other on opposite sides of the axial passage 40b of the said fixture. The coupling-lugs 9595 of the. cylinderand bayonet-mounting fixture 99 are adapted to be entered into coupling-notches 96-96 provided diametrically opposite each other in the periphery of the flange Mb of the barrel llib of the firearm. The coupling-notches 9696 respectively receive the couplinglugs 95-95 of the fixture 94 when the latter is mounted in place on the barrel 16b, with its rear end abutting against the forward face of the flange Mb, in which position the said fixture 94 is securely retained by thev annular nut 42b, all as has been more clearly set forth in the description of Figs. 1 to 12 inclusive. It will thus be seen that the cylinder and bayonet-mounting fixture 99 is effectively held against rotation with respect to the barrel l6b by employing means such as the coupling-lugs 9595 and their complemental coupling-notches 96-46.

By means of a construction such as "is hereinshown and described, it is possible to locate the gas port leading radially from the bore of the barrel, closely adjacent the forward end of the *barrel, without requiring the undue lengthening of thestructure in order to provide for the mounting of a bayonet. Furthermore, a fixture such as the fixture '39 serves not only to provide a gascylinder of rugged construction and a sturdy bayonet-support if desired, but also provides .a rigid fixture forwardlyof the stock to shield the same and to which a stacking-swivel may be attached.

By means of the construction herein described and shown in the accompanying drawings, it will be seen that the cylinder may be readily removed and that by the removal of the said cylinder, the gas-port 55 and passage 53 may be readily cleaned by the use of any suitable object being passed upwardly through the passage 53a formed axially in line therewith in the lower wall cf the cylinder-receiving passage 95- and that the pas- I sage 53a is normally effectively closed off by the cylinder 56. A

It will also be seen that the cylinderand bayonet-mounting fixture is accurately positioned with respect to the port 55 and that the said iii! ture is effectively prevented against turning with respect to the barrel Hi. The cylinderand bayonet-mounting fixture thus serves to provide teristics of ,the invention, and the present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.

We claim: i

' 1. A gas-operated-automatie firearm-construction including in combination: a barrel having an axial bore and a gas-port leading laterally therefrom; cylinder-limiting means carried by the said barrel; a cylinder-mounting fixture having a barrel-receiving passage extending therethrough from front to rear and receiving .the muzzle portion of the said barrel, a cylinderreceiving passage extending from front to rear in substantial parallelism with the said barrelreceiving passage, and a gas-port extendingthrough a wall of the said cylinder-mounting fixture into communication with the gas-port of the said barrel; means for holding the said cylintier-mounting fixture against both rotary, and axial displacement with respect tothe said barrel; a tubular gas-cylinder removably and replaceably installed in the cylinder-receiving passage of the said cylinder-mounting fixture and having a radial gas-port in communication with the gas-port in the wall of the cylinder-receiving passage of the said fixture, the said tubular gas cylinder having a longitudinal clearance-groove flanked at either side by an end wall, c said clearance-groove receiving the cylinder-limiting means of the said barrel and the end walls of the said clearance-groove being positioned to en-- gage with the cylinder-limiting means of the said barrel to limit the rotational movement of the said tubular gas-cylinder in the cylinder-receivmg passage of the said cylinder-mounting fixture; and locking-means for releasably coupling the said tubular gas-cylinder to the said cylinder mounting fixture against axial displacement with respect thereto and constructed and arranged to receiving passage, and a gas-port extending through a wall of the said cylinder-mounting fixtureginto communication with the gas-port of the said barrel; a positioning-nut threaded upon the said barrel and holding the said cylindermounting. fixture against forward axial displace.- ment withrespect thereto; means for holding the said cylinder-mounting fixture against rotary displacement with respect to the said barrel; a tubular gas-cylinder r'emovably and replaceably installed in the cylinder-receiving passage of the said cylinder-mounting fixture and having a, ra-

'dial gas-port in communication with the gasport in the wall of the-cylinder-receiving passage of the said fixture, the said tubular gasylinder having on its periphery a longitudinal clearancegroove flanked at either side by an end wall, the

said clearance-groove receiving the locating-nut on the said barrel and the end walls of the said clearance-groove'being positioned to engage with the said locating-nut of the said barrel to limit be rendered effective and ineffective respectively the rotational movement oi. the said gas-cylinder by reverse turning movements of the said gasin the cylinder-receiving passage of the said flxcylinder with respect to the said cylinder mountture; and locking-means for releasably coupling ing fixture. p the said tubular gas-cylinder to the said cylinder- 5 DAVID M. WILLIAMS.

- mountiniflxture against axial displacement with WILHAM C. ROEMER.

respect thereto and constructed and arranged to 

